The invention is concerned with container closures generally, and in a specific embodiment the invention relates to a medical test jar, sealed with an agar inside and with provision for injection of blood or other serum for testing the serum. The invention is particularly concerned with a sealing closure for such a test jar, the test jar and closure being of all plastic construction, of a conveniently large size, capable of sustaining a vacuum and the closure being easily removable by laboratory personnel.
Medical test jars for the general purpose stated above are known. The jars themselves have typically been very small, on the order of test-tube size, with an agar-holding paddle extending down into the container. The jars have typically been inconveniently small in size and have required handling of the paddle by the technician to conduct testing operations. In these tests the moldable, gelatin-like agar on the paddle generally holds a culture medium to be used in a test of the injected serum, often a different agar on each side of the paddle. Another reagent solution generally is carried in the jar below.
There have been certain problems with conventional agar closure and paddle assemblies, both in use and in the economy of their manufacture.
These medical test jars often are under vacuum, for example a vacuum of about 5 to 10 inches of mercury. The need for vacuum raises certain issues regarding sealing of the test jar with a screw-on closure, given the objectives of providing a clear, transparent container which will not leak vacuum, and with a means for retaining the agar on the test paddle, to resist falling off the paddle even during jarring in transportation or handling of the test assembly.
The test container itself can advantageously be made of a highly transparent plastic material, OPET (oriented polyethyltetrathiolate), a relatively new material developed for superior oxygen barrier properties.
The oriented PET has a tendency to sink to some degree along one axis by cold flow down the line of the orientation, over a period of time. This tends to occur at two locations on the container finish. As an example, a container with a 53 mm finish opening can sink 0.007 inch over time, at two opposed locations, creating an undulating shape at the top edge of the finish. Such cold flow sagging or sinking makes a greater demand on the integrity of the seal between the closure and the container, particularly with vacuum to be retained. If a one-piece closure is used, with a sealing gasket fixed to its underside, very high level of application torque will be required to form a seal sufficient to maintain a vacuum, which would require unacceptably high torque to remove the closure. The high static friction of the gasket material against the lip or rim of the container finish must be overcome to unscrew and release the gasket from the container. Even though the vacuum inside the container may be reduced or essentially released (by injection of the blood or serum) at the time the closure is to be unscrewed, the need to retain the vacuum and the nature of the OPET as cold flowing with time, will require a very high torque closure.
In addition to this a fixed sealing gasket is normally adhered to the cap by glue. The high level of application torque combined with the high level of frictional resistance on the top of bottle neck finish will tend to twist the gasket material which in turn will have the effect of loosening the cap (back off) caused by the memory of the gasket material. Moreover, unless a rubbery gasket is used, conventional cap lining materials will not be able to provide much of a shelf life and adjust to the anticipated sink in the OPET surface.
A conventional valve seal molded into the one-piece cap also requires a very high level of application torque to form a vacuum tight seal. This will relax somewhat due to cold flow; however, a high level of removal torque is required to unscrew the cap which level is beyond the strength of the average person. In practice it has been found by the applicant that a vacuum can be maintained in this way with an application torque of 40 inch-pounds, but the 35 inch-pounds required to remove it was beyond the average person. Moreover, this method has no compensation for sink in the bottle neck and would undoubtedly lose vacuum over time as this phenomenon occurred.
Under these conditions it is simply beyond the capability of an ordinary, integrally formed valve seal on a relatively hard plastic closure, to retain the vacuum for an appreciable shelf life, such as one year.
Further, the internal vacuum to which the agar on the paddle is subjected tends to cause the agar to shrink somewhat, due to the tendency of the vacuum to remove oxygen (or moisture) from the agar. This causes the agar to shrink away from any retention device included on the paddle, so that retention of the agar becomes more difficult.
At the same time, the agar paddle must be retained very stably to some suitable structure of the closure.
The closure must also provide for injection of the blood or other serum essentially without interrupting the seal of the assembly.
The following U.S. Patents show multiple-piece closures for containers, some having relevance to certain aspects of the invention described below: Miller U.S. Pat. Nos. 3,339,772, Manske 3,736,899, Claasen 3,831,796, Picoy et al. 3,946,891, Wolkonsky 4,493,427, Ryder 4,605,135, Taragna et al. 4,664,276, Grabenkort 4,948,000, Conard 5,080,245, and Schumacher 5,269,429.
None of the above patents discloses a medical test jar having the features described below, nor does any describe a two-piece closure with a closure ring and a connected but freely rotatable separate gasket which enables high-integrity sealing on a container without requiring high torque in closing and opening the container.